# A simple RISC-V emulator

This is a toy emulator for RISC-V, made for educational purposes.
The goal is to have a base rv32i instruction set (the bare minimum) plus a M-extension for division and multiplication. In theory, it should be enough to execute simple C programs compiled with GCC and sprinkled with a few linker scripts. Of course, no libc because there's no OS.

## Compiling and running

You'd need [nix package manager](https://nixos.org/) in order to build the project. This is because installing cross-toolchain to compile an example project is difficult, and I don't know of other ways except nix that make it easy.

If you don't have it, install it like this:

```sh
curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install
```

Now, to build the emulator:

```sh
nix develop

eval "$configurePhase"
ninja
```

As a result you should get an executable called `rve`

## Cross-toolchain and an example program in C

There is an example program which you can compile. It requires some custom toolchain so currently not built with CMake. To compile it:

```sh
cd example
make
```

As a result, you'll get an `example.raw` binary. To execute it:

```sh
./rve ../example/example.raw
```

The expected output of the example program is `40320`.